lib: Add kconfiglib code

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

lib/kconfiglib/olddefconfig.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python3
+
+# Copyright (c) 2018-2019, Ulf Magnusson
+# SPDX-License-Identifier: ISC
+
+"""
+Updates an old .config file or creates a new one, by filling in default values
+for all new symbols. This is the same as picking the default selection for all
+symbols in oldconfig, or entering the menuconfig interface and immediately
+saving.
+
+The default input/output filename is '.config'. A different filename can be
+passed in the KCONFIG_CONFIG environment variable.
+
+When overwriting a configuration file, the old version is saved to
+<filename>.old (e.g. .config.old).
+"""
+import kconfiglib
+
+
+def main():
+    kconf = kconfiglib.standard_kconfig(__doc__)
+    print(kconf.load_config())
+    print(kconf.write_config())
+
+
+if __name__ == "__main__":
+    main()